1. Field of the Invention
The present invention relates to a corrosion barrier coating composition, and more particularly to a corrosion barrier coating composition comprising an admixture of (1) a one-component epoxy resin composition, (2) polytetrafluoroethylene (TEFLON) powder, and (3) glass powder. The present invention is also directed to a substrate coated with the corrosion barrier coating composition of the invention, and a method of coating a substrate with the corrosion barrier coating composition of the invention.
2. Brief Description of the Art
Corrosion barrier coatings are useful in a wide variety of industrial applications to provide metal parts with protection from natural elements such as water, carbon dioxide, salts spray, oxygen, ozone, UV radiation, and the like. In particular, corrosion barrier coatings have proven useful in aircraft and industrial equipment, where severe environmental conditions can occur. For example, aircraft fuel and oil pump housings frequently require repair because they corrode during use. This corrosion reduces the longevity of the housings and results in costly rebuilding, repair, or replacement.
The prior art is replete with corrosion-inhibiting compositions for use in a variety of purposes. However, most of these compositions provide only a thin coating of corrosion barrier to the substrate. While thin coatings may offer adequate protection against corrosion, the thin nature of the barrier makes them more susceptible to damage and corresponding loss of corrosion protection in the damaged area.
Representative patents describing corrosion inhibiting coatings include the following:
U.S. Pat. No. 4,996,085 discloses coating a pump housing surface with a composition comprising a hardenable epoxy resin, a reinforcing filler, and an agent having a lower coefficient of friction than the epoxy resin. Graphite may function as the reinforcing filler, and the frictional reducing agent may be either graphite, in fibrous or granulated form; fluorinated carbon (i.e., --(CF.sub.x)-- wherein x&lt;2); or molybdenum disulfide. Further, the preferred class of epoxy resin is a diglycidyl ether of a dihydric phenol (e.g., the diglycidyl ether of bisphenol A).
U.S. Pat. No. 5,316,790 discloses a lubricative coating and filler material for restoring metal surfaces that have become scratched, scored, grooved, or otherwise damaged to a functional condition. This coating and filler material is a mixture of an epoxy resin, tungsten disulfide, and isopropyl alcohol in a ratio of 9:1:1.6.
U.S. Pat. Nos. 5,603,818 and 5,385,655 disclose a method of producing an adherent and corrosion-inhibiting multilayer coating on metal parts by electrolizing a first composition made from water emulsions, dispersions, or solutions based on water-dispersible or emulsifiable synthetic resin such as alkyd resins, acrylic polymers, melamine resins, and the like. A second coating, comprising at least one film-forming organic resin, is applied over the first coating.
U.S. Pat. No.5,753,316 discloses a method of treating metal surfaces by coating those surfaces with a film-forming sealcoat containing at least one organic resin and at least one torque modifier. The organic resin is made from water emulsions, dispersions, or solutions based on water-dispersible or emulsifiable synthetic resin such as alkyd resins, acrylic polymers, melamine resins, and the like. The torque modifier may be one or more fluoroalkene polymers, polyethylene, polypropylene, mica, talc, or calcium carbonate.
U.S. Pat. No. 5,312,491 discloses a rust-inhibiting composition containing oxime-based rust converter compounds formulated with a latex based paint to provide a flexible film coating that acts as a barrier to oxygen and water vapor diffusion to the metal surface.
Copending U.S. patent application Ser. No. 08/568,114 discloses a curable composition useful for repairing worn surfaces on housings comprising an admixture of (1) a mixture of (a) at least one one-component epoxy resin, (b) at least one solvent and (c) at least one reactive diluent, wherein the epoxy resin is present in a major (i.e., at least 50% by weight) amount in the mixture; (2) graphite powder; and (3) polytetrafluoroethylene powder.
Copending U.S. patent application Ser. No. 09/413,566 discloses a low friction coating composition, comprising about 60 wt % to about 95 wt % of a high temperature epoxy, comprising (1) about 30 wt % to about 60 wt % of N,N'-m-phenylene dimaleimide; (2) about 30 wt % to about 60 wt % of bisphenol epoxy resin; and (3) about 1 wt % to about 5 wt % of amorphous silicon dioxide; (B) about 1 wt % to about 30 wt % of molybdenum disulfide; and (C) about 1 wt % to about 20 wt % of polyimide powder.
While these corrosion-inhibiting and low-friction coating materials may be satisfactory for certain applications, there is still need for improved corrosion barrier compositions that are useful on a wide variety of substrates, such as housings of various aircraft and machinery parts, that are exposed to severe environmental conditions. The present invention is believed to be an answer to that need.